All the world is a stage in “Circle Mirror Transformation,” now running at Old Academy Players. Instructor Marty conducts a creative acting class, and a sequence of vignettes interlace so meaningfully we ourselves are transformed by play’s end.

Marty conducts a bunch of exercises that put herself and four would-be thespians through their paces. All five lie on their backs and repeat numbers from one to 10. They form circles, sometimes mimic each other’s movements, sometimes ad lib words to a developing sentence. They pair off to argue, where nonsense language is secondary to body language. And they take on the roles of their classmates, telling their life stories.

“Circle” is masterful in its gathering intensity. Actors portray student actors who are, first and foremost, role-less people. Irony suffuses the play. Marty’s exercises, designed to put her charges authentically in the moment, take a back seat to the students’ own lives, so comically and painfully present.

Director Loretta Lucy Miller trusts a cast that proves unerringly believable. Sarah Labov shines as Marty. The teacher is the only self-assured person in the classroom, yet you sense a vulnerability that dramatically emerges at the end. In still another ironic twist, it turns out the teacher has the most to learn.

Theresa (Jennifer Shorstein) is an amateur actress in retreat from New York, and Schultz (T.J.Doyle) is a carpenter. Both on the rebound, they have a fling. Marty’s husband, James (Joseph Tranchitella) has dark secrets, and Lauren (Maya Knell) is a high school junior, delightfully incapable of disguising her feelings.

You will never see a show where minimal staging is more expressive. The set is an unadorned dance studio in Shirley, Vermont. The fourth wall is an imaginary mirror. When the actors leave, the bare and silent stage is a haunting metaphor for the emptiness that threatens their lives. Equally, clothes are at first unremarkable. But as you get to know these people, you feel no other individual could possibly wear them.

Annie Baker, a 36-year-old playwright, has already won a Pulitzer Prize for “The Flick” and numerous other awards, including an Obie for “Circle Mirror Transformation.” All her works are similar, halting characters who slowly come to know their own desires and those of others.

In “Circle,” you have no sense of the little New England town. Along with praise, Baker has been criticized for her small, enclosed worlds. Some see her as a theater miniaturist with no larger field of concern. But this miniature world carries metaphorical force.

You come to care deeply about her comic-tragic characters, and you worry that they never will make genuine, lasting connections. How different is that from the self-deception, fear, game-playing and misalliances you read about in the media in that larger world Annie Baker is accused of ignoring?

Old Academy Players is located at 3544 Old Indian Queen Lane in East Falls. “Circle Mirror Transformation” will run through Jan 28. Reservations at 215-843-1109.